The present invention relates to a computer system, and more particularly to a file server that provides a plurality of networked clients with file services.
Technologies for sharing data among a plurality of networked computers have been developed since the 1980s. One of the most popular data sharing technologies is Sun Microsystems's NFS (Network File System). NFS is described briefly in “UNIX Internals: The New Frontiers” (written by Uresh Vahalia, translated by Hideyuki Tokuda, Akira Nakamura, Yoshihito Tobe, and Yoshiyuki Tuda, published by Pearson Education, 2000). NFS is a technology for managing data on a file basis. A computer in which files are saved is called a file server, and a computer that uses the files saved in a file server via a network is called a client. NFS is a technology that allows the user to use files saved in the file server as if they were saved in the client's disk. In practice, NFS is defined as a network communication protocol between a file server and a client.
As network computing has rapidly become popular in recent years, technologies for a secondary storage unit directly connectable to an IP network such as a LAN have been proposed. They include NetSCSI, NASD (Network Attached Secure Disks), and an ISCSI standard defined by IETF (Internet Engineering Task Force). NetSCSI and NASD are described in detail in “File Server Scaling with Network-Attached Secure Disks” (written by Garth A. Gibson et. al, Research paper “THE 1997 ACM SIGMETRICS INTERNATIONAL CONFERENCE ON MEASUREMENT AND MODELING OF COMPUTER SYSTEMS, pp. 272-284). iSCSI is a standard that allows SCSI (Small Computer System Interface) protocol communication to be performed on a network. This is described in detail in “Internet Draft iSCSI” (written by Julian Satran, et. al, 2002).
FIG. 2 shows the configuration common to NetSCSI and NASD. In the system shown in FIG. 2, clients 101 that receive file services, hard disk drives 103 in which data is saved, and a file control unit 105 that manages and controls the hard disk drives 103 are connected to a LAN 100. The hard disk drive 103 comprises a magnetic disk medium 106 on which data is recorded and a disk control unit 107 that communicates with devices connected to the LAN 100 and records data on the magnetic disk medium 106 in response to an instruction from other devices. In addition to the usual data read/write control function, the disk control unit 107 has an authentication controller 108 that permits or inhibits communication with other devices connected to the LAN 100. The authentication controller 108 has authentication information 109 on the devices with which communication is permitted. The file control unit 105 comprises a LAN controller 114 that performs communication on the LAN, a file system 115 that provides the clients 101 with data on the hard disk drive 103 as a file, and an access controller 116 that controls the authority to access the hard disk drive 103. According to the description in “File Server Scaling with Network-Attached Secure Disks” (written by Garth A. Gibson et. al, Research paper “THE 1997 ACM SIGMETRICS INTERNATIONAL CONFERENCE ON MEASUREMENT AND MODELING OF COMPUTER SYSTEMS, pp. 272-284, the operation of the system in FIG. 2 is roughly as follows.
The client 101 sends a file access instruction to the file control unit 105. In response to the file access instruction, the file system 115 in the file control unit 105 analyzes the request from the client 101 and issues a data input/output instruction to the hard disk drive 103 to or from which data is written or read. In response to the input/output instruction, the hard disk drive 103 transfers data with the client 101 who issued the file access instruction. Upon completion of data transfer, the hard disk drive 103 informs the file control unit 105 that the data transfer has been completed. In response to the data transfer completion information, the file control unit 105 informs the client 101 that the file access instruction has been completed.
The hard disk drive 103 communicates also with the clients 101. Therefore, it has the authentication controller 108 for certificating clients. The file control unit 105 has the access controller 116 that determines the security policy of the hard disk drives 103.
“File Server Scaling with Network-Attached Secure Disks” (written by Garth A. Gibson et. al, Research paper “THE 1997 ACM SIGMETRICS INTERNATIONAL CONFERENCE ON MEASUREMENT AND MODELING OF COMPUTER SYSTEMS, pp. 272-284) also discloses a technology for encrypting communication between the file control unit 105 and the hard disk drive 103 and for generating virtual communication channels. This prevents the clients 101 from wiretap communication between the file control unit 105 and the hard disk drive 103.
In addition, the filer server unit has no display or keyboard; instead, the user usually operates the file server unit from a management terminal connected to the LAN 100.